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E39 (1997 - 2003) The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

About 10 months ago I replaced the thermo, waterpump, upper/lower hoses, coolant sensor, fan switch, and expansion tank with refresh kit from ESC. A couple months ago the temp needle would spike, but the red light wouldn't turn on. After scanning through different forum posts I decided to re-bleed the system. That worked for about a week. Fast forward to 2 weeks ago, I went ahead and started throwing parts at her hoping for the best. New fan clutch, thermo, waterpump, expansion tank hoses, fan blade, and all has been good for the past 2 weeks, or so I thought. I was idling in the pickup line to get my boys from school, and damn it, it happened again. Before leaving the house today I just happened to check my oil and while there checked my coolant level, and the expansion tank is empty. WTF? There are no leaks from the hoses or the radiator that I can see, however, there are small puddles of coolant behind the alt. and above the OFH in some of those checkered crevices. I know I should take it somewhere to have it properly diagnosed, but was wondering if there's something I'm missing that you can can suggest I check myself. I hear a slight hiss after turning the engine off somewhere down and behind the oil filter canister. BTW, i changed my oil 1200 miles ago and it was just regular old dirty oil. Sorry for the wall of text, but I'm a bit peeved and frustrated at the moment. Thanks in advance for any help or advice you can give.

That hiss is a leak when the system is pressurized. The empty expansion tank confirms you are losing coolant and the puddles are evidence of a leak. Take the bottom pan off. Remove the fan shroud for better access. Put newspaper under the fron end. Then warm the car up and then shut it off. Look for the hissing sound. It should also be visible. Look directly above any spot on the newspaper that is wet. It should be pretty easy to find.

These engines have a couple of plastic pipe-hoses tucked underneath the intake manifold and behind the OFH. More and more, I'm seeing threads about these two hoses leaking. You can't remove/replace them without pulling the intake manifold (and OFH, and alternator) because they are coming out of the engine block and otherwise inaccessible.

These engines have a couple of plastic pipe-hoses tucked underneath the intake manifold and behind the OFH. More and more, I'm seeing threads about these two hoses leaking. You can't remove/replace them without pulling the intake manifold (and OFH, and alternator) because they are coming out of the engine block and otherwise inaccessible.

Here's a shot of an M54 block with those two pipes still attached.

Thanks for all the replies! After refilling the expansion tank today i drove over to see the guys at Avenue Autosport in Port Charlotte. Their business focuses mostly on hot roddin Audi/VW, but do a fair amount of everything German. I explained everything I had already done, and broke out my Surefire Fury light to show them what I was seeing with respect to coolant puddles. He instantly blurted out that it was 1 of those hoses your pic shows, and said that he's seen quite a few failures like this. He spotted a dryed out section of the pipe and even a bit of coolant just below. Anywho, he said I'll be perfectly fine as long as I keep the coolant full until a week from this Friday, when I can get in to have it done. What a relief! I mentioned cracked/warped head, and he just laughed at the thought. Told me story of some woman who just came through the shop last week with no belts on her E39 after driving almost 100 miles with the temp needle in the red the whole way. She apparently hit something and broke off the power steering pulley somehow. They put everything back together and it is as good as new. The engine was still solid, since there was plenty of coolant left in the block. I trust him and what he knows, so when he said that these engines can take a hell of a beating before they crack or warp, I believe him. Glad it's something small, even if I did overreact a little. Thank you all for your help. Btw, I never saw any of those pipes in any of the diy or realoem diagrams before, so i guess there's still more to this cursed cooling system than I thought. I guess I didn't have to re-replace all those cooling system parts like I did afterall, but at least i get another year out of them. I'll post the final results after it's done, including part#'s and cost.
Thanks again everyone

(That's for a 528i M52TU engine but probably identical to yours in this area. You can back up and enter your VIN or car details to get specifics. The section is engine cooling, under engine.)

Regardless of what the AutoSport man says, these pipes are aging plastic. One may be leaking now but if it decides to open up, it will release coolant very quickly and your engine could overheat before you realize it. Sorry to shake your faith, but these i6 engines will blow a head very quickly if you let them overheat.

If you have another car, you should consider driving that one until this one is fixed. That's my 2 cents.

(That's for a 528i M52TU engine but probably identical to yours in this area. You can back up and enter your VIN or car details to get specifics. The section is engine cooling, under engine.)

Regardless of what the AutoSport man says, these pipes are aging plastic. One may be leaking now but if it decides to open up, it will release coolant very quickly and your engine could overheat before you realize it. Sorry to shake your faith, but these i6 engines will blow a head very quickly if you let them overheat.

If you have another car, you should consider driving that one until this one is fixed. That's my 2 cents.

...Told me story of some woman who just came through the shop last week with no belts on her E39 after driving almost 100 miles with the temp needle in the red the whole way. She apparently hit something and broke off the power steering pulley somehow. They put everything back together and it is as good as new. The engine was still solid, since there was plenty of coolant left in the block. I trust him and what he knows, so when he said that these engines can take a hell of a beating before they crack or warp, I believe him...

Anyone who says an E39 M52/M54 engine is fine after an overheat needs to see a psychiatrist.

I read somwhere that on the first 528 models, those 2 waterpipes were aluminum? If that's the case would they fit on the M54 engine? The first batch of 528 (e39) do NOT have this problem, or so I read somwhere on one of the forums. Maybe CNN can chime in and confirm/deny?

P.S.: forget about it. just took a peek at realoem, and the layout is totally different. So there's the answer.

Anyone who says an E39 M52/M54 engine is fine after an overheat needs to see a psychiatrist.

I know, but I'm trying to remain positive to get me through the next week and a half. I've been driving like this for the past 2 months or so, and now that I know what the problem is she'll probably let me down. I'm going to go online tonight and buy the pieces I need, so I don't have to wait for the Doctor to confirm the prognosis, and then tell me it will take a couple days to get the parts. Just need to figure out what all is needed. Since it looks like the manifold needs to come off I'm also thinking about the CCV, although I don't have any symptoms and it seems to fail more in cold weather climates. Might as well, right?

I am in the middle of the coolant pipes now.
I have removed the alternator, the oil filter housing, air intake stuff.
And need the remove the intake manifold. Once all that is out of the way
it looks fairly easy to swap out the coolant pipes.
My car is 2000 528it and has 160K. The first cooling refresh
was about 80K ago. They did not do the plastic coolant pipes. I now
have a small leak from the upper pipe. I am doing the CCV while in there.
When it is all done I think nearly every trouble spot has been addressed.

If my transmission holds up another 100 K I will be overjoyed.
The previous owner has done 2 transmission filters and fluid so far.

So it looks like the alu return pipes (used in the 528) are also prone to leakage. Thread

Quote:

Originally Posted by ChevyTruckGuy78

ok im looking around i got 4.10 gears and wanna put a lsd in for more traction for winter driving and just more traction. im not looking to break the bank just trying to se what the cheapest route is im not into racing or drifting this thing got 202k on it and just looking for more traction its a 97 and yes im new to bmw's but been a gas tech for over 16 years and diesel tech for last 5 light duty and med duty trucks are my thing but i got this car for next to nuttin and drives great got m5 65 rims on it and the guy sank tons of money into it trying to fix a coolant leak which was a return line under the intake.